Many companies make the same mistake every year assuming their torque tools are accurate and in working order. They also assume factory torque charts are correct and a certified gauge ensures tool accuracy. It’s a hazardous assumption because calibrated power tools frequently are not performing as expected.

Although there are other ways of establishing the tension on a bolt, torque is used most often. Such tools include hydraulic and electric torque wrenches, torque multipliers, and manual wrenches. After the required yearly calibration, tool owners usually get a certificate detailing the particulars which also verifies the quality of the equipment.

Technicians with mobile calibration equipment say they can calibrate all makes and models of torque wrenches up to 25,000 ft-lb. The computer, just behind the Mobil- Cal technician, lets him sign into the company’s online system, identify the tools that need calibration, and follow the step-by-step ISO procedures for the task.

Certificates are also needed after turbine assembly. For instance, during mechanical-completion inspections, inspectors with OEMs must work through punch lists. The OEM inspector will look for training records and calibration sheets for the tools used. Also, internal quality reviews conducted by companies will need to see the calibration sheets. What’s more, companies go through a process to become ISO certified and having a documented calibration process is part of ISO procedures.

Most technicians keep the calibration forms handy in a three-ring binder–kept…somewhere. If proof of certification cannot be produced, the technician may be forbidden to use the tool on the job site until it is. That could be a problem for the technician who may have to resort to a manual tool for the day, and accept a significant loss of productivity.

Engineers at Alltite Total Bolting Solutions may have an answer to the problem in an online service that tracks tools, their calibration, and certification. One goal is to get rid of the easily lost certification forms and make them more readily accessible.

The MobileCal sample calibration report lists the values measured and calculated for a hydraulic torque wrench.

For example, the Customer Portal-Calibration chart lists all the tools in a particular facility. “This could be a single wind farm, a region, or all the tools that need calibration for a particular company,” says Alltite CEO Tom Smith (alltite.net). He adds that the program was devised with two sides in mind. On the calibration technician’s side, data and procedures assist with calibrating torque tools step-by-step to ISO standards 6789 and 17025.

Clients, says Smith, see and manage all their calibrations through the online portal. A user name and password lets customers access the data. Customers search by their calibration ID, printed on a sticker placed on their tool at the last calibration. Users might also search by calibration-due date, or the tool and equipment type. Smith says the program can be customized for particular needs.

Benefits are that the company’s quality-control person would see the entire fleet of tools to make sure they are compliant. The paperless system lets users get away from chasing the sheet of paper that usually comes with calibrations.

An alternative method at some large companies is to send equipment to its lab where it’s calibrated and sent back with a folded sheet of paper or calibration certificate. But the wind industry is so wide spread, says Smith, a technician could be in Pennsylvania one week and Minnesota the next. “If he’s hunting down this piece of paper, he’s losing time and money. With this system he can log into the portal, find the tool in question, pull up the certification in standard or metric units, and print or download it. It’s also viewable on smart phones.

The Expires column on the Calibrations and Search page of Alltite’s TorqueWare customer portal tells which tool in the fleet is next up for calibration.

The calibration reports show measured and calculated values, such as the torque to pressure ratio, as-found readings, as-left readings (after adjustments), serial number of the wrench, and more. “Another plus is it provides a quality program for an entire organization,” says Smith. “With the online system, it drives consistency across all business units and eliminates variance by having a single quality program. Without something like it, a company with 15 different sites could have 15 different vendors and possibly gaps in their quality program. This program wraps all calibration, certifications, and documentation into a single point which give clarity and consistency to the organization.

The portal also gives an inventory list so companies can allocate their resources. For instance, one site may have half of a company’s torque equipment, when in fact it’s more needed elsewhere. Smith says he’s yet to find a company that can track all its tools, and is 100% accurate. A frequent discovery, for example, is that more than 65% of clicker torque wrenches don’t meet OEM specifications.

WPE

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Fasteners with tension indicators: Most bolts in a wind turbine are manufactured to OEM specs. The OEM also provides a torque value which the construction crew must apply to each bolt for a required level of tension. But because torque does not always correlate to bolt tension, bolt manufacturers have devised a range of devices for indicating tension.

One particular bolt design has an indicator cap on its head. Until the cap turns by hand with difficulty, the bolt is under tensioned. The device works by drilling out part of the bolt center and installing a tension indicator link to the cap. When tensioned, the bolt elongates, tightening the link and preventing the cap from rotating under finger pressure. Another design places a visual indicator in the bolt head. When the indicator is out of position, the bolt is under or over tensioned. The feature makes checking for tension a brief visual task.

Why torque control is a questionable way to achieve consistent pretension in structural bolts comes down to friction or what’s known as the k-factor. This is the relationship between the torque applied to a fastener assembly and the actual tension produced in the bolt. A short form of the relationship is:

Tension = Torque/kd where: k = k-factor, and d = diameter
K-factors vary from lot to lot, from bolt to bolt within a lot, and as a consequence of handling, storage, and lubrication. K-factors can range from 0.10 to over 0.20. Also, consider the variability of the torque tool. Manufacturers of tension indicators say it is likely that when using torque control to govern bolt tension that actual bolt tensions will vary ±40% or more.

Most industrial-fastener problems come from a bolt, cap screw, or spindle nut that has failed in service due to vibration, thermal cycling, or other harsh environment conditions. A few bolt manufacturers will design a prototype solutions and manufacture a locking system to accommodate load, corrosion, clearance, and material requirements. Customers, however, will have to test the prototypes to assure performance. Shaker or fatigue tests can often point to a best design when several are available. Users will be expected to specify the material, preload, and torque for their fastener applications.

A preassembled pair of washers provides a structural, self-locking fastener that prevents bolted joints from loosening by shock or vibration in high-stress applications. The device consists of two preassembled (glued for easier handling) washer-shaped pieces. Each has an inclined cam on one side and a series of ridges on the other. On installation, the cam sides are mated and placed between nut and joint material. Under vibration, the nut tries to rotate loose but, because the angle of the cams is greater than the pitch angle of the bolt thread, the interlocking cams and the non-slip ridges of the washer work together to create a jam which prevents loosening. The washer pair can also be used on bolts in either blind-holes or through-holes. In blind-holes, the washer pair is placed under the bolt head, while through-hole applications use the washers beneath a nut.

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Greg Palmer, Director of Marketing at Reid Supply, says the company is constantly improving their product category offerings to help their customers find the exact product that they need, without the need to do a lot of shopping around.

“IMTS allows us to showcase some of the literally tens-of-thousands of items available in our new 900 page catalog and thousands more on our website,” says Palmer. “Plus, show attendees get to pick our brains to help them solve problems with product ideas that they may not have considered.”

This year the company will be showing new products in the categories of Knobs, Handles and Hand Wheels; Clamps and Workholding; Fasteners and Hardware; Bearings and Power Transmission; Maintenance, Repair and Operations (MRO); and Safety.

“Each year we have a good selection of new products, like the Hurricone floor drying system, which combines a wet floor caution cone with a battery-powered floor dryer,” says Palmer.

Since 1948, Reid has supplied customers with both hard-to-find and everyday products to help them build their industrial business. Those customer’s who have shopped with company for decades know the value of this kind of longevity.

Not only will Reid Supply highlight new products at the annual IMTS show, they will also showcase their free CAD drawings of over 90% of their catalog products on their website at ReidSupply.com.

Reid Supply
www.ReidSupply.com

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